Composite paper sheet



July 10, 1956 w. A. HERMANSON COMPOSITE PAPER SHEET Filed April 21, 1952IN VENTOR Mam A. Ham/M00 BY W ATTORNEY United States Patent COMPOSITEPAPER SHEET William A. Hermanson, Brookline, Mass. Application April 21,1952, Serial No. 283,367 5 Claims. (Cl. 154-54) The present inventionrelates to a composite cellulose sheet used as soft flexible padding forvarious purposes. The present invention is particularly useful in theprotecting of highly polished and highly finished surfaces both inshipment and in use and it may also be used in protecting suchmerchandise as glass, pottery, furniture and other items fromscratching, chipping, denting, cracking or from damage in many otherways.

The present invention is an improvement over the composite sheet shownin my prior Patent No. 2,200,171, and also in the copending applicationin which I am a co-inventor, Serial No. 166,826, filed June 8, 1950,issued December 16, 1952, as United States Letters Patent No. 2,622,051.

While in the copending application mentioned above,

the pad therein described is provided with spaced areas which are raisedabove other areas cemented to a backing sheet, in the present inventionthe backing sheet and the other sheets may be continuously cemented overtheir entire area, or the other sheets may be fluted, corrugated orarranged to be adhered to the backing intervals. One of the difficultieswhich is encountered in manufacturing composite protective pads orsheets of the present invention is that the adhesive used for cementingthe sheets or Webs together pentrate too rapidly and completely thegroup of sheets so that they lose some sheet at spaced of their soft,flexible, yielding and protective characterisi tics in the finishedproduct.

It is one of the purposes of the present invention to control the actionof the adhesive so that the composite sheet retains all of the qualitiesof the individual sheets as if they were laid together without anyadhesive being.

used. This is accomplished in the present invention by using diflerenttypes of sheets in face contact with the backing sheet from the type ofsheet which comes in contact with the surface to be protected. Theseintermediate sheets are latently absorbent and permit smaller adhesiveparticles or only a percent of the adhesive to penetrate through thelatently absorbent sheets in suflicient space distribution to providethe cementing of the highly absorbent cellulosic top sheets together andto the latently absorbent sheet or sheets lying against the back of thesheet. By controlling the penetration of the adhesive from the surfaceof the back sheet through the latently absorbent sheets and through thehighly absorbent cellulosic sheets the resultant composite pad remainssoft, pliable, flexible, yieldable without any indication of hardnessusually caused at the places of cementation.

A latently absorbent sheet may be defined as one which is partiallysized in such a way that the absorption through the material is gradualin time and not particularly rapid so that liquid adhesive willpenetrate the web while drying thereby having an appreciably smallerarea covered by the adhesive on the side of the sheet opposite to thatwhere the adhesive was applied than on the side where it was applied.Such sizing which may be slack sizing may be accomplished by the use ofrosin,

ice

wax emulsions, starch, hydroxyethylcellulose, carbozymethylcellulose,halogenated-siloxanes and other suitable types of slack sizing. Theseintermediate sheets are also preferably manufactured'from a differentproduct than the top sheets both for cheapness and for the purpose forwhich they are used. The intermediate sheets next to the backing sheetmay be blended of waste paper stock with a small fraction of absorbentsulphate or sulphite fiber pulp. The top sheets should be highlyabsorbent and soft.

In the ordinary course of producing a composite sheet, the sheets arerun through a pressure roller after the backing sheet has had adhesiveapplied to it. The squeezing between the pressure rollers of the sheetsusually force adhesive from the backing sheet through to the top sheetsso that the structure of the composite sheet is not uniform in surfacetexture and not suitable for the intended purpose.

With sheets composed as briefly set forth above, it is possible to runthe sheets with the adhesive applied to the backing sheet through thepressure rolls and produce a composite sheet which has all the desiredchar acteristics of a perfect sheet for the intended purpose.

Without further describing the merits and advantages of the presentinvention, the invention will be more fully described in connection withthe drawings illustrating an embodiment thereof, in which:

Figure 1 shows in exploded form the composition of the composite sheetforming the subject of the present invention, and,

Figure 2 shows somewhat in diagrammatic form a section taken through thecomposite sheet when the composite sheet is made up as a parallellycorrugated sheet adhered along spaced intervals to the backing sheet.

Both figures are somewhat diagrammatic since they are upon an enlargedscale due to the difiiculty of showing the elements clearly inproportionate sizes.

In Figure 1, 1 indicates a backing sheet which may be any type of paperor paper composition material such for instance as kraft paper, fabric,thin cardboard or ordinary strong paper. This backing sheet ispreferably of a closed formation and may be treated to provide Wetstrength and other durable properties. Next to the backing sheet 1 aresheets 2 and 3 which are latently absorptive of partly closed formation,sized with rosin or other suitable sizing or slack sizing materials,which sheets are preferably made of a blend of a waste paper stock witha small fraction of absorbent sulphite or sulphate cellulose fibers. Forlow cost it is preferable to use such a blend of waste paper stock witha small fraction 10%20% of sulphite or sulphate. The latent absorbencyof the sheet may be controlled by a combi nation of such materials sinceif more sizing is used this will offset the absorbent action of thesulphite or sulphate fibers and the sizing may also be used, to effectthe desirable partly closed formation. By partly closed formation ismeant a formation in which the openings in the sheet are comparativelysmall and will not pass large size adhesive particles which are appliedto the backing sheet. Such adhesive particles pass through the latentlyabsorbent sheet either by pure mechanical action of being squeezedthrough a partially open formation or by true absorbency of the latentlyabsorbent sheets in penetrating by capillary action and adsorbtion thefibers and structure of the sheet. Using a waste paper stock with lowsulphite and sulphate content, this absorbency is materially delayed sothat while the particles of adhesive are pressed and forced through thepartly closed formations of the sheet the adhesive is not soaked up bythe sheet and therefore the surfaces of the sheet lying against thelight thin creped cellulose sheets 4, 5 and 6, are only spotted atspaced intervals with the adhesive which form a suliicient bond to holdthe sheets together but not to effect the charcateristics of the web.While only three such top sheets are shown in Figure l, more than threesuch sheets are used. Figure 2 shows five such sheets indicated bynumerals 4, 5, 6, 7 and 8. On

, the surface of sheet 1 there is applied preferably a paste adhesive 9,composed preferably of starch or other suitable material. Such adhesiveis formed of various size particles, some of see Figure 2, and somelarge, as illustrated by 11. The top sheets 4-3 inclusive are composedof cellulose material of thin low tensile strength, extremely absorbent,creped, flexible, unhydrated, unsized fibers of very open formationhaving a percentage of creping in excess of 25%. These sheets are formedand creped prior to making the composite sheet. Such creped sheets arefed from rolls to the pressure rollers simultaneously with the latentlyabsorbent sheets 2 and 3 which may be slightly creped as for instanceless than 25% and the backing sheet 1 to which the adhesive is applied.These webs may be combined into a flat sheet or as shown in Figure 2,they may be combined in a corrugated sheet in which both the latentlyabsorbent sheets, slightly creped, if desired, and creped sheetsare'corrugated just prior to the time they are applied to the backingsheet. The adhesive lying between the faces of the backing sheet and thelatently absorbent sheets is forced by pressure and by the latentlyabsorbent action of the latently absorbent sheets through the sheets andprovide a substantial spot cementation as indicated by the spots 12, 12,12 dispersed and spaced in the sheets 4, 5, 6, 7 and 8. These sheets areso highly absorbent and of such open web construction that the particlesof adhesive which penetrate the latently absorbent sheets are almostinstantaneously dispersed among the creped highly absorbent cellulosewebs forming the top of the composite sheet or pad.

When the composite sheet is made in corrugated form as indicated inFigure 2, the adhesive in the area not in contact with the latentlyabsorbent sheets, dry and'simply form a film or coating on the backingsheets in these areas, but since the sheet is covered, this has noeffect upon the composite sheet.

As an example of the materials forming the composite sheet, I have usedfor the top creped open formation, a cellulosic sheet of a 12 poundweight based on 500 sheets, 24" x 36" dimension. For the latentlyabsorbent sheets I have used a 32 pound sheet on the basis of 500sheets, 24" x 36" dimension. The top open web highly absorbent sheetwill absorb approximately -20 times their weight of water. Latentabsorbency is usually which are small as illustrated by 10,

measured on a time basis. In the present instance it is necessary thatthe adhesive does not penetrate through the top sheets of the compositesheet during the time that it is passing through the rolls which jointhe sheets together.

Having now described my invention, I claim:

1. A composite sheet comprising a backing sheet of relatively closedformation heavier than the other sheets forming the composite sheet, anintermediate sheet lying in face contact with the backing sheet and aplurality of thin, low tensile strength, extremely absorbent creped,flexible, unhydrated, unsized, cellulosic webs, forming the top sheetsof very open formation having a percentage of creping of approximately25% lying over said intermediate sheet, said interrnediate sheet beingof higher tensile strength, heavier and having a less open formationthan said webs and being latently absorbent and sufficient adhesiveapplied to the face of the backing sheet whereby only enough of it willpenetrate the intermediate sheet to spot cement the open webs togetherand tothe intermediate and backing sheets without afiecting the visiblecharacteristics of the web. 7

2. A composite sheet as in claim 1 in which two similar intermediatesheets are laid together between the backing sheet and the openformation top sheets. 7

3. A composite sheet as in claim 1 in which the top sheets are sulphatecellulose pulp webs and the intermediate sheet has from 10% to 30%sulphate cellulose pulp.

4. A composite sheet as in claim 1, in which the top sheets are sulphitecellulose pulp webs and the intermediate sheet has from 10% to 30% pulp.

5. A composite sheet, comprising a multiple set of thin, low tensilestrength, extremely absorbent, creped, flexible, unhydrated, unsized,cellulosic webs of very open formation, having a percentage of crepingin excess of 25%, in combination with at least one Web of higher tensilestrength, latently absorbent creped, flexible, cellulosic webs ofpartially closed formation, having a percentage of creping less than25%, means forming said set of webs in parallel fluting with said set ofwebs being bonded in parallel lines between said flutings, to acellulosic, hydrated, sized backing sheet of closed formation.

sulphite cellulose References Cited in the file of this patent UNITEDSTATES PATENTS 1,556,575 Armstrong Oct. 13, 1925 2,226,553 Cross Dec.31, 1940 2,622,051 Hermanson et al Dec. 16, 1952

1. A COMPOSITE SHEET COMPRISING A BACKING SHEET OF RELATIVELY CLOSEDFORMATION HEAVIER THAN THE OTHER SHEETS FORMING THE COMPOSITE SHEET, ANINTERMEDIATE SHEET LYING IN FACE CONTACT WITH THE BACKING SHEET AND APLURALITY OF THIN, LOW TENSILE STRENGTH, EXTREMELY ABSORBENT CREPED,FLEXIBLE, UNHYDRATED, UNSIZED, CELLULOSIC WEBS, FORMING THE TOP SHEETSOF VERY OPEN FORMATION HAVING A PERCENTAGE OF CREPING OF APPROXIMATELY25% LYING OVER SAID INTERMEDIATE SHEET, SAID INTERMEDIATE SHEET BEING OFHIGHER TENSILE STRENGTH, HEAVIER AND HAVING A LESS OPEN FORMATION THANSAID WEBS AND BEING LATENTLY ABSORBENT AND SUFFICIENT ADHESIVE APPLIEDTO THE FACE OF THE BACKING SHEET WHEREBY ONLY ENOUGH OF IT WILLPENETRATE THE INTERMEDIATE SHEET TO SPOT CEMENT THE OPEN WEBS TOGETHERAND TO THE INTERMEDIATE AND BACKING SHEETS WITHOUT AFFECTING THE VISIBLECHARACTERISTICS OF THE WEB.